The present invention relates to the field of identification bar codes and scanners and more particularly, is directed to a bar code stencil and method of using such a stencil to integrally embed a bar code into an article during its manufacture. The stencil may also be used in a post production or after market identification procedure for bar code marking of articles.
The development of modern bar codes began in the 1940s in response to the food industry's need for a reliable and economical system for inventory control and for automatically reading product information at grocery store check outs. The first patent to issue on such a system is believed to be U.S. Pat. No. 2,612,994 entitled "Classifying Apparatus and Method" and which issued on Oct. 7, 1952.
Although the coding system used in the '994 patent relied on a series of concentric circles to encode the identification information, the original coding approach developed by the inventors was a series of narrow and wide vertical lines much like present day bar code systems. Early implementations of the concentric circle approach proved unreliable however, as the circles were difficult to print without smearing. Smeared circles introduced reading errors when scanned and thus were unacceptable. The use of vertical bars eliminated the smearing problem and associated scanning errors.
Since the adoption of the Universal Product Code (UPC) in 1973, bar codes have proliferated to virtually all areas of article and product identification. Bar codes are now widely recognized as an economical and reliable identification system.
Over the years, a number of different versions of the UPC bar code have been developed. Version A is one of the most popular and is illustrated in FIG. 1. The Version A format includes a plurality of spaced vertical bars 1 which form the bar code and a plurality of human readable digits which correspond to the bar code, i.e, "0 25528 43507 3" as indicted by reference number 2.
As shown in FIG. 1, the code is divided into 12 digits, with the first digit 3 being usually a "0". The next five digits 4 are assigned to the product manufacturer by the Uniform Code Council and thus serve to identify the manufacturer. Accordingly, all of the bar codes for the same manufacturer will have this same five digits. The next five digits 5 represent the item identification code given to a particular product by the manufacture. Thus, 99,999 products can be uniquely identified. The final twelfth digit 6 is a check digit which is used by the bar code scanner to confirm the accuracy of the scan.
Each of the human readable digits is encoded into the code using a two-part binary coding system as indicated in the table below:
Code Key Digit Left Right Value Binary Code Binary Code 0 0001101 1110010 1 0011001 1100110 2 0010011 1101100 3 0111101 1000010 4 0100011 1011100 5 0110001 1001110 6 0101111 1010000 7 0111011 1000100 8 0110111 1001000 9 0001011 1110100
Each "1" in the key code is represented by a black bar 7 as illustrated in FIG. 1 and each "0" in the key code is represented by a white or space 8. There is a center code of four lines (binary digits 01010) which bisect the bar code. On the left side of the bar code, the Left Binary Code digits from the above table are used and on the right side of the bar code, the Right Binary Code digits from the table are used. This mirror image coding technique allows the scanner to read the number code in either direction. Start and stop codes are used by the scanner to set the width of the binary digits within the bar code symbol. The scanner also uses the check digit to calculate a check sum as is know in the art. If the correct check sum is not calculated, the bar code read is rejected.
FIG. 2 is a further illustration of a typical UPC bar code with its constituent parts labeled.
As a testament to the popularity of bar code use, the UPC bar code is scheduled to be phased out by the year 2005 because its 12-digit length will no longer be sufficient to handle the demand for bar codes. In its place, the United States is expected to adopt a version of the European Article Numbering (EAN) system. The EAN bar code system has thirteen digits and can thus accommodate substantially more product identifications than the UPC.
The traditional printed bar code system continues to serve its original purpose of grocery store inventory control and check out very well. Bar codes formed of conventional two-dimensional printed bars work well where the article to be labeled is not subject to a harsh environment and the bar code label is not likely to be rubbed off or smeared over so that it can not be read.
The food industry serves as an ideal environment for conventional bar codes. Bar codes used for food labeling are unlikely to be subjected to harsh environments due to the inherent need to prevent adulteration and damage to the food package. Thus, the bar code label is not likely to become damaged or unreadable.
The bar code system has in some respects however, become the victim of its own success. Today, attempts are being made to use bar codes in many environments in which a conventional printed two-dimensional bar code, such as the one used for food products, can not be used. One such environment is the tire manufacturing industry.
U.S. Pat. No. 5,160,383 assigned to Goodyear Tire & Rubber discloses one example of the use of a bar code labeling technique in the tire industry. According to the patent, it is important that a tire label be highly durable so that it may still be read after many years of tire service and multiple retreading. The patent also notes that serial numbers can be molded into tire side walls but that doing so is labor intensive and costly. Thus, Goodyear sought to improve upon conventional tire labeling systems by attaching an identification label to the rubber inter lining of an uncured tire. The label is made of two materials which are co-curable with the rubber of the tire. The tire is then cured using a conventional curing process which results in the label becoming permanently affixed to the inside of the tire.
Goodyear also is the assignee of U.S. Pat. No. 4,625,101 which discloses a method of molding a bar code configuration onto the sidewall of a tire. The bar code configuration has a plurality of sloped reflective surfaces which allow more flexibility in locating the bar code scanner without adversely effecting the accuracy of the scan. A bar code plate mold insert is used to mold the bar code configuration into the side wall of the tire during the vulcanization process.
Another technique for labeling a tire is disclosed in U.S. Pat. No. 4,941,522 assigned to the Yokohama Rubber Company. The Yokohama approach involves an improved bar code plate mold insert which is also used to mold a bar code into a side wall of the tire during the vulcanization process. The improved plate is said to solve the problem of deterioration of the tire's resistance to weather in the area of the molded bar code.
Like the tire manufacturing industry, bar code labels also have great utility in other harsh environments as well. For example, domestic metal casters cast and ship millions of tons of product each year. An effective way to identify each product for tracking and inventory control purposes is to label it with a bar code. Because casts usually are subjected to a post casting process to finish and shape them to their final form, a conventional printed bar code label is often difficult to apply to a casting surface and is also subject to being rubbed off or covered over during the subsequent finishing process. Moreover, a printed bar code label is likely to deteriorate over time, well before the end of the life of the cast it self, making the bar code difficult or impossible to read.
Ideally, an identification bar code will be embedded into the article during the manufacturing process. Doing so, avoids the possibility of mis-identification, i.e., the wrong bar code being applied, in a subsequent labeling step.
In order to improve the durability and readability of bar codes in harsh environments such as casting, a three dimensional bar code construction was developed. An end view of a portion of such a bar code is illustrated in FIG. 3. Each bar has a width 30 and a height 31. The distinguishing feature of this type of bar code is its height 31. The bar code is scanned by a three dimensional bar code reader which detects the presence or absence of a bar based on its height rather than its contrast as a conventional two dimensional bar code reader does. Thus, a three dimensional bar code can be read when no contrast is available. Three dimensional bar code readers are known in the art, and include the readers manufactured by Sensis Corporation for reading Bumpy Bar Codes.TM..
Three dimensional bar codes have proved to be a much better choice in some situations as they will not easily rub off, smear, peel or vanish. They can be painted over or the article on which they are placed can be subjected to various treatment processes without the readability of the bar code being adversely affected. Three dimensional bar codes are also useful where a traditional printed bar code label will not adhere to the surface of the article to be labeled.
The use of bar codes during manufacture for work-in-process tracking, inventory control, work piece routing, etc., has become a valuable tool. Embedding the bar code into the article during its manufacture is the most expedient and cost effective identification system. However, due to the harsh environments in which many manufacturing processes occur, embedding a bar code into a manufactured article can present a challenge. The challenge usually involves overcoming the ill effects caused by the very high temperatures and pressures that are present in, e.g, cast and molding processes. Thus, there is a need in the art for a bar code stencil which can be easily and reliably used for embedding bar codes into articles during their manufacture.